Thorn Grove Preserve lies directly east of Thorn Creek Woods Nature Preserve between Park Forest and Steger. Starting with a five-acre donation in 1988, it has grown to 136 acres. Predominantly woodland, it also includes amphibian breeding habitat in vernal (springtime) depressions, wetlands, and ponds. There is currently no public access or facilities.
Ongoing preservation efforts work toward protecting interior woodland habitat by reducing fragmentation through expanding and buffering the grove, and toward gaining hydrological control of ponds and wetlands that extend beyond the boundaries. Long-term planning will look at enhanced connections or new linkages to other public open space on Thorn and Deer Creeks.